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1. Kīlauea magma chamber inflation triggered strong 2007 earthquakes

Hawaii's Kīlauea volcano has been erupting since 1983. Starting in 2003, researchers noticed an inflation of the magma chamber beneath the volcano, an inflation that accelerated in 2006. In June 2007, the volcano's eruption peaked with a burst of activity known as the Father's Day event. In the buildup to the Father's Day eruptions, according to new research by Wauthier et al., a pair of large-magnitude earthquakes hit, with an epicenter beneath the volcano. Earthquakes are common around the volcano, which sits on Hawaii's Big Island, but with magnitudes of 4.7 and 4.1, the two 2007 earthquakes were among the most powerful recorded in the region since records began in 1959.

Most volcano-tectonic earthquakes have very small magnitudes, and no known mechanisms exist to explain the powerful Kīlauea earthquakes. Analyzing a range of seismic and geodetic data, the authors suggest that the large-magnitude quakes were caused when inflation in the magma chamber beneath Kīlauea caused preexisting faults to slip. The authors suggest that a similar mechanism could play out at other volcanoes worldwide.

Icy conditions make it difficult to monitor the southern part of the Southern Ocean using floats or ship-based sampling. For about a decade scientists have been mounting temperature and salinity sensors on the heads of seals from several colonies around Antarctica. There is now a fairly large data set of seal-derived hydrographic data.

Roquet et al. sought to determine how valuable these data are in studying ocean conditions. They conducted two numerical ocean circulation experiments, one using data from a global network of floats to constrain the model and one also using seal-based data. The only difference between the two experiments was the inclusion of the seal-based data.

The authors find that including the seal-derived data modified the estimated circulation patterns and improved the model's agreement with satellite data on sea ice concentrations. They conclude that sensors mounted on animals can provide a valuable contribution to monitoring polar conditions.

Although it is not possible to predict when an earthquake will occur, many earthquakes have been found to have had some precursor activity. To study precursors of stick-slip behavior, Johnson et al. conducted laboratory experiments on a sheared granular material under normal stress ranging from 2 to 8 megapascals (290 to 1,160 pounds per square inch) as an analog for a fault under tectonic stress. They find that acoustic emissions and microslips are a precursor to larger movements. Very similar results are obtained in a discrete element simulation of sheared beads. These types of experiments could help scientists better understand when earthquakes are more likely to occur. As shown by a number of researchers, very similar activity preceding faulting can occur in the Earth.

People in northern Utah, including Salt Lake City, depend on water stored as winter snow and delivered by mountain streams to populated areas. Climate models predict that in the near future, warmer temperatures will lead to a decrease in winter snow and streamflow in mountain streams, possibly leading to water shortages for the region.

To gain a longer-term perspective on water availability, it is helpful to have a record of past streamflow variability, but streamflow records are generally limited to relatively short term instrumental records. Allen et al. reconstructed streamflow in the Logan River--a main tributary of the Bear River that is the main source of inflow to the Great Salt Lake--for the past several centuries, going back to 1605. Their reconstruction, based on tree ring records from Douglas fir, pinyon pine, and Rocky Mountain juniper trees, indicates that streamflow was more variable, with more extreme droughts and floods, over the past several centuries than in the recent instrumental record. The authors suggest that water resources managers should take this higher variability into account when planning water management strategies.

In 2002, Antarctica's Larsen B Ice Shelf disintegrated over the course of just a few months. The shelf, which covered more than 3000 square kilometers (1158 square miles) of ice, had been stable for thousands of years before it broke up, and the processes involved in the sudden breakup were not well understood. Before the breakup, there were more than 2700 small supraglacial lakes on top of the ice shelf that had formed as ice melted gradually over the preceding years. Observations indicated that the majority of those lakes drained within the final few days before the ice shelf broke up, but scientists were not certain how that could have happened.

Now, using a simulation of the stresses that the lakes create on the ice shelf, Banwell et al. show that the draining of one supraglacial lake could result in fractures under other lakes, which, in turn, could cause more fractures under more lakes and thus cause numerous lakes to drain, in a chain reaction. The draining of many supraglacial lakes in a short time period ultimately led to the breakup of the entire ice shelf, the authors suggest.

Lakes emit carbon dioxide and methane and are thus an important part of global climate. Many estimates of emissions for individual lakes are based on a measurement from a single location within the lake, but, as Schilder et al. point out, emissions can vary across the lake. They collected methane and carbon dioxide measurements at several locations for each of 32 lakes in Europe, and find that estimates based only on near-shore measurements tend to underestimate diffusive emissions, while those based only on center-lake locations tend to overestimate emissions. The study provides a method to improve estimates of greenhouse gas emissions from lakes.

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